At the present time, there are a wide variety of toothbrush designs. These designs are based on a number of different theories. At one time, it was considered desirable to have hard bristles for a toothbrush. However, it was then feared that these hard bristles would result in excessive wear of the tooth enamel adjacent to the gingival margin. This was expected to occur, due to the backward and forward motion employed by many people to clean their teeth.
It was then proposed to use relatively soft bristles. The intention with soft bristles is that they will cause thorough cleaning of all tooth surfaces, etc., whilst at the same time not being so hard as to cause excessive abrasion. However, from experience it has been found that such soft-bristled toothbrushes do not always adequately clean a person's teeth.
A particular problem occurs with the teeth surfaces adjacent to the gingival margin and interproximal areas. These areas are most prone to the build up of plaque. Accordingly, the cleaning materials and techniques used should be such as to ensure adequate cleaning of these areas, without causing excessive abrasion, etc.
It is also desirable that a toothbrush should massage and invigorate the gums. However, soft-bristled toothbrushes again do not adequately massage the gums, to improve circulation, etc.